U.S. patent number 4,149,253 [Application Number 05/740,260] was granted by the patent office on 1979-04-10 for soil compacting apparatus.
This patent grant is currently assigned to Losenhausen Maschinenbau AG. Invention is credited to Fritz Konig, Alois Paar.
United States Patent |
4,149,253 |
Paar , et al. |
April 10, 1979 |
Soil compacting apparatus
Abstract
A soil compactor has (1) an apparatus preceding it to measure
characteristics of the soil significant to the compaction
operation, and/or (2) an apparatus following it to measure
characteristics of the soil after compaction. The soil compactor
has one or more controls over the compaction operation. The
controls are operated in accordance with the measurement
indications of said apparatus.
Inventors: |
Paar; Alois (Cologne,
DE), Konig; Fritz (Wuppertal-Elberfeld,
DE) |
Assignee: |
Losenhausen Maschinenbau AG
(Dusseldorf-Grafenberg, DE)
|
Family
ID: |
25760080 |
Appl.
No.: |
05/740,260 |
Filed: |
November 10, 1976 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
390512 |
Aug 22, 1973 |
|
|
|
|
199275 |
Nov 16, 1971 |
|
|
|
|
Foreign Application Priority Data
|
|
|
|
|
Nov 21, 1970 [DE] |
|
|
2057279 |
|
Current U.S.
Class: |
701/50; 404/117;
404/122; 404/84.05; 700/275 |
Current CPC
Class: |
E02D
3/026 (20130101); E02D 3/02 (20130101) |
Current International
Class: |
E02D
3/00 (20060101); E02D 3/02 (20060101); G05B
011/06 (); E01C 019/28 () |
Field of
Search: |
;404/117,84,122,133
;364/505,506,508,424,425 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
659237 |
|
Mar 1938 |
|
DE2 |
|
822979 |
|
Oct 1951 |
|
DE |
|
852667 |
|
Aug 1952 |
|
DE |
|
1634616 |
|
Jul 1970 |
|
DE |
|
222708 |
|
Jul 1968 |
|
SU |
|
Primary Examiner: Gruber; Felix D.
Attorney, Agent or Firm: Darbo & Vandenburgh
Parent Case Text
RELATED APPLICATION
This application is a division of our prior application Ser. No.
390,512, filed Aug. 22, 1973, now abandoned, which was a division
of our prior application Ser. No. 199,275, filed Nov. 16, 1971, now
abandoned.
Claims
We claim:
1. A soil compacting apparatus movable along a path and having a
compacting element, control means by which at least one of the
operational parameters determining the compacting action by said
soil compacting apparatus may be varied and measuring means
responsive to a selected physical parameter of the soil, the
improvement comprising:
said measuing means trailing said compacting element and moved by
the soil compacting apparatus along said path after the soil on the
path has been acted upon by the compacting element and producing a
measured value signal related to the degree of compaction of the
soil in said path;
said control means including an adjustable fixed-value transmitter
for producing a command signal;
adding means connected to receive said command signal and said
measured value signal to produce a difference output signal
therefrom;
transfer signal generating means to generate a transfer signal
relating a change in said difference output signal to the
corresponding change in said at least one operational
parameter;
a multiplier stage having two inputs, means connecting a first of
its inputs to said adding means and the second of its inputs to
said transfer signal generating means so that said multiplier stage
receives said difference output signal and said transfer signal and
produces a control signal;
a converter connected to receive said control signal and generating
a driving signal for adjusting said at least one operational
parameter of said soil compacting apparatus in accordance with said
control signal,
whereby said at least one operational parameter may be varied in
response to said measured value signal to produce a relatively
uniform compaction of said oil in said path as said soil compacting
apparatus moves along said path.
2. A soil compacting apparatus as set forth in claim 1, wherein
said transfer signal is a fixed voltage.
3. A soil compacting apparatus as set forth in claim 2, including
another measuring means leading said compacting element and
connected to and moved by the soil compacting apparatus along said
path before the soil in the path has been acted upon by the
compacting element, said other measuring means including a
measuring transducer for producing another measured-value signal
related to a selected physical characteristic of the soil, delay
means for producing a time-delay in a signal received thereby,
means connecting the delay means to the other measuring means for
supplying said other measured-value signal to said delay means
whereby said delay means produces a time-delayed,
other-measured-value signal, and means connecting said delay means
to said adding means to supply said time-delayed,
other-measured-value signal to said adding means so that said
difference output signal is modified thereby.
4. A soil compacting apparatus as set forth in claim 3, wherein
said selected physical characteristic is the degree of compaction
of the soil.
5. A soil compacting apparatus as set forth in claim 3, wherein
said selected physical characteristic is water content of the
soil.
6. A soil compacting apparatus as set forth in claim 3, wherein the
two measuring means are spaced a given distance apart and the
time-delay of said delay means corresponds to the time required for
the apparatus to traverse a distance corresponding to said given
distance.
7. A soil compacting apparatus as set forth in claim 1,
including generator means having a trigger input and producing a
command feed-forward signal when a signal is received at said
trigger input;
wherein said adding means comprises
a first adding element having two inputs and an output one of which
inputs receives said command signal and the other of which inputs
is connected to receive said command feed-forward signal, said
adding element supplying said command signal to said output and
additionally said command feed-forward signal when a signal is
received at said trigger input of said generator means, and
an adding stage having two inputs and an output one of which inputs
is connected to said adding element output and the other of which
is connected to receive said measured value signal, said adding
stage producing said difference output signal at the output
thereof; and
wherein said transfer signal generating means comprises
pulse triggered timer means having a trigger input and a pulse
output and having a set time equal to one said command feed-forward
signal pulse,
pulse generator means having minimum value limiting connected to
receive said difference output signal and to produce an output
pulse,
means connecting the pulse generator means to said trigger inputs
of said command feed-forward signal generator means and said timer
means,
first store means having a reset input connected to the pulse
output of said timer means and an input connected to said output of
said adding element to receive said command signal therefrom,
second store means having a reset input connected to the pulse
output of said timer means and a signal input,
means connecting said signal input of said second store means to
said measuring means for supplying said measured signal to said
second store means,
a second adding element connected to said first store means and to
the output of said first adding element for producing a difference
signal,
a third adding element connected to said second store means and to
said means connecting said second store means and said measuring
means to receive said measured signal for producing a difference
signal,
another multiplier stage connected to said second and third adding
elements to receive said difference signals therefrom for producing
said transfer signal,
a timer controlled gate connected to receive said output pulse from
said pulse triggered timer means and rendered nonconductive during
the set time thereof, said gate having an input and an output,
means connecting said gate input to said other multiplier stage to
supply said transfer-signal to said gate input,
a transfer signal holding element connected to the output of said
gate, and
means connecting said transfer signal holding element to said
second input of the first mentioned multiplier stage.
8. A soil compacting apparatus as set forth in claim 7,
wherein said adding stage has a third input, and
including another measuring means leading said compacting element
and connected to and moved by the soil compacting apparatus along
said path before the soil in the path has been acted upon by the
compacting element, said other measuring means including a
measuring transducer for producing another measured-value signal
related to a selected physical characteristic of the soil, delay
means for producing a time-delay in a signal received thereby,
means connecting the delay means to the other measuring means for
supplying said other measured-value signal to said delay means
whereby said delay means produces a time-delayed, other
measured-value signal, and means connecting said delay means to
said third input of said adding stage to supply said time-delayed,
other-measured-value signal to said adding stage so that said
difference output signal is modified thereby.
9. A soil compacting apparatus as set forth in claim 8, wherein
said selected physical characteristic is the degree of compaction
of the soil.
10. A soil compacting as set forth in claim 8, wherein said
selected physical characteristic is water content of the soil.
11. A soil compacting apparatus as set forth in claim 8, wherein
the two measuring means are spaced a given distance apart and the
time-delay of said delay means corresponds to the time required for
the apparatus to traverse a distance corresponding to said given
distance.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to soil compacting apparatus in which one or
more operational characteristics such as the rotational speed of
the exciter, the unbalance, the direction of force or the traveling
velocity may be varied and which has measuring means and adjusting
means for varying the operational characteristics, which adjusting
means may be influenced in accordance with the signal delivered by
said measuring means.
Soil compacting apparatus, in particular apparatus in which the
soil is compacted by vibrations, such as plate vibrators and
rollers with vibrating barrels are frequently provided with
systems, known in the prior art, by means of which the kind,
magnitude and duration of the effects produced by the apparatus on
the soil which is to be compacted may be adjusted either in steps
or continuously; for example, such systems may vary the velocity at
which the apparatus is driven or pulled over the soil which is to
be compacted or they may vary to the magnitude of the centrifugal
force exerted by such apparatus. The said force may be altered in
compacting apparatus with unbalance excitation by means of the
unbalance, the excitation rate being retained, and it may also be
varied together with the rotational speed of the exciter; it is
also possible to vary the unbalance and rotational speed of the
exciter relative to each other so that a new vibrator frequency is
obtained with the same vibration intensity. In addition to varying
the aforementioned two characteristics it is also possible to vary
the principal direction of the centrifugal force of a working part,
either by pivoting the exciter or by phase displacement between the
rotors in the case of exciters with two or more mass force
generators. The phase relationships of the vibrations of soil
compacting apparatus with a plurality of working parts may also be
varied, for example in a first setting to produce a simultaneous
maximum action on the soil or in a second setting to produce an
alternating effect.
Experience has shown that the kind of soil compacting apparatus,
which may be adjusted in the manner described hereinabove, do not
provide optimum compacting results on all soils if the previously
mentioned operating parameters are fixedly defined, but that
instead it is advantageous for a high vibration frequency to be
applied to one soil while a low centrifugal force is more
advantageous for another soil and a sliding rather than pressing
stress is more advantageous for yet another soil. Manufacturers of
dynamic soil compacting apparatus therefore provide adjusting means
of the kind mentioned heretofore to provide a wider range of
applications for such apparatus and to render them universally
usable.
In practice there are however substantial difficulties which
militate against the envisaged technical progress being achieved.
The first and basic reason is due to the fact that the
relationships between the action produced by the compacting
apparatus on the soil and the displacement phenomena which occur as
the result of such action are substantially unknown: according to
the prior art, the user is not yet in a position to optimize the
vibrator frequency of the apparatus in accordance with accessible
soil properties such as particle distribution and water content
based on experience or in terms of a mathematical formula.
A further reason is due to the relationship between the vibration
technological characteristics of the soil compactor and a change,
for example, of the centrifugal force. Most dynamic soil compacting
apparatus operate by so-called "jump" progress, that is to say, the
exciter force raises the working parts from the soil in certain
phases; the parts then perform a ballistic motion initiated by the
exciter force and strike the ground at a moment of time which is
defined substantially by the laws of free fall, at which time the
exciter force is not necessarily orientated towards the soil. This
synchronism between impact pulse and simultaneous exciter force,
frequently desirable for intensive compacting, can be disturbed by
even slight changes - including increases - of the unbalance or
centrifugal force so that the "so-called" jump characteristics of
the affected working part which defines compaction may experience
fundamental changes which cannot be quantitatively controlled.
Finally, there are also certain properties of the bulk itself which
is to be compacted which may prevent the desired success being
achieved even if the aforementioned problems are assumed to have
been solved. The intrinsic dry bulk density of a dumped material
fluctuates, rarely less than 3% and frequently more than 5% and
this also applies to local differences of water content. The
initial fluctuations are retained almost unchanged after final
compactions at Proctor values not substantially in excess of 100%
if the dumped material is uniformly worked with a compacting
apparatus; the final density, assuming a uniform initial bulk
density, is practically proportional to the local water content
since this, in the same way as in the Proctor test, has a
noticeable effect on the compaction achieved with a defined
compacting energy. If steps are to be taken to ensure that minimum
dry bulk weight values are obtained for a given compacting problem,
these fluctuations must be added to the test value, which, although
it amounts to only a few percent, nevertheless results in a
substantial increase of the work input.
Proposals have been made according to which the adjustment of
suitable machine parts or the variation of their characteristic
values is related to measured values which are recorded during the
compacting operation. A first apparatus of this kind comprises a
seismic acceleration pick-up disposed on a working part, subjected
to superimposed loading, and manually operated means for varying
the rotational speed of the exciter; it is desirable for the said
rotational speed to be maintained at or close to the value at which
the acceleration pick-up delivers its maximum signal, that is to
say, the system comprising the working part and the soil being
approximately at resonance under the effect of the periodic exciter
force. The disadvantages of this solution to the problem are not
only the basic limitation to the control of superimposed load
working parts - resonance conditions do not apply to jump operation
either in terms of appearance or by way of concept - but also the
fact that co-control of the exciter force through the rotational
speed and due to the frequently super-critical damping resulting
from friction in the soil it is not possible for the resonance to
become sufficiently clearly defined and in these cases there is no
adequately significant matching criterion for manual
regulation.
It has also been proposed to measure the impact energy of a dynamic
soil compacting apparatus component which functions in jump
operation for the purpose of controlling the traveling velocity of
the apparatus relative to said measurement. A common feature of the
proposals is the idea of utilizing the operating characteristics of
the compacting apparatus as a controlled condition in terms of
process control technology, the compactness produced by the
apparatus being the "desired value". Such solutions to the problem
suffer from the defect that the relationship between the "desired
value" and the appropriate controlled condition is hypothetical
because, despite intensive research, it has not been possible to
establish a generally valid relationship between the dry bulk
density of a soil on the one hand and the vibration characteristics
of a dynamic compacting apparatus operated on said soil. Apparatus
of this kind therefore merely shift the problem of determining
suitable operational parameters of the compacting apparatus, that
is to say, defining the relationship between these two magnitudes
in a specific, individual case. Although progress is achieved, the
problem is not yet solved but its extent is merely limited and
expressed in concrete terms.
The object of the present invention is to provide means for varying
the operating parameters of soil compacting apparatus during
operation based on measurements but in conditions which are free of
previous limitations; this includes primarily the process-dependent
relationship to the superimposed loading or "jump" operation of the
compacting apparatus or its working parts and the condition of
validity of the relationships between measured value and "desired
value" which must be defined, tested and allowed for independently
of the apparatus in question.
The invention is based on the idea to arrange the methods for
recording measured values so that on the one hand they become
independent of the vibration characteristics of the apparatus or
its working parts and on the other hand can be related to soil
characteristics, relevant to output, more directly than this is
possible according to the prior art.
In this sense it is a further object of the invention to
differentiate the solution of the general problem in accordance
with different performance features, for example, relative to the
compressive strength or shear strength in addition to the
compactibility.
According to the basic idea of the invention, the measuring means
are constructed as measuring transducer for physical soil
characteristics of the soil which is to be compacted or which is to
be partially or solely compacted.
According to the invention, the vibration characteristics of the
soil compacting apparatus are not utilized as controlled condition
as in the prior art but the physical soil characteristics
themselves are utilized to function as controlled condition.
The invention may be performed by trailing measuring means being
provided which are constructed as measuring transducers for
detecting physical soil characteristics after a pass of the soil
compacting apparatus. This is not genuine regulation since the soil
compactor operation characteristics, influencing the compaction of
the soil which is to be freshly compacted, are varied in accordance
with the characteristics of the soil which has already been
compacted, this change of the operating characteristics of course
having no further effect on the characteristics of the soil which
is already compacted. Nevertheless, the method may be employed
since generally it is possible to assume a degree of constancy of
the soil characteristics.
The trailing measuring means may be constructed as measuring
transducer for one or more of the following physical soil
characteristics after the passage of the compacting apparatus or
individual working parts thereof:
(a) compactibility
(b) coefficient of soil reaction
(c) shear strength
(d) continuous vibration impedance
(e) pulse or impact impedance
(f) penetrometric properties of the soil surface
(g) set of the soil surface.
One or more command signals may be transmissible to the final
control means in the manner of command values in process control
technology, the signals of the measuring transducers and the
command signals being connected in opposition to each other in an
adding stage and, where appropriate, being adapted to act through a
control amplifier on the final control means.
Finally the object of the invention is to achieve the desired
advance, possible, according to the prior art, only by utilizing
hypotheses on the relationship between the measured value and the
desired value by adopting a solution to this problem of the unknown
part of the controlled apparatus.
In this connection the invention is based on the principle that
advantageous or optimum adjustment of the operational parameters of
dynamic soil compacting apparatus cannot be achieved with means and
models of conventional process control technology owing to the
special features of the particular art in question. Process control
technology is based throughout on a knowledge of the relationship
between measured value and final control value, that is to say, the
characteristic of the controlled apparatus and only in this way is
it possible for the control deviation to form the final control
value which will sensibly drive the functional value in terms of
magnitude and direction to the reference value. In the present
case, the soil to be compacted represents at least part of the
controlled apparatus and is therefore variable not only from
building site to building site but also within individual
compacting areas and furthermore it has a noticeable effect on the
operating characteristics of the apparatus and moreover defines its
reaction to changes of the final control element, for example, the
throttle of the prime mover for controlling the rotational
speed.
A further embodiment of the invention therefore provides that
supplementary signals of very low frequency may be additively
superimposed on the command signals and a transfer signal is formed
by a multiplier from the changed command signal and the measuring
transducer signal changed thereby through the controller and the
controlled part of the apparatus, the said transfer signal being
adapted to vary the transfer coefficient of the controller through
another multiplier.
The following means may be used for measuring the compactibility of
the soil before, after and during the pass of the compacting
apparatus:
Radio isotope measurements with gamma rays; in this measuring
system a receiver measures the intensity of the reflected radiation
which expresses the moist bulk density of the soil by reference to
a relationship which must be empirically determined and which is
practically independent of the soil. Since it is not necessary for
these means to be manually moved it is possible for shieldings to
be thicker than those of conventional field probes and accordingly
it enables sources to be employed which have activities higher than
20 mC and thus enable the integration periods for the receiver
pulses to be reduced. This method may be combined in known manner
with corresponding measurement of back scattered thermal neutrons
to enable the dry bulk weight to be displayed.
Measurement of the electric soil resistance by means of a
four-probe system. The said four-probes are preferably formed by
four substantially disc-shaped members with semicircularly radiused
edges, electrically insulated from each other and guided on a
common shaft. They are rolled over the measuring position with a
corresponding slight pressure. The current passing through the
outer probes and required to maintain a controlled voltage between
the inner probes is a clear measure for the dry bulk weight if the
water content is known.
A test ram or a test baulk, bearing hydraulically on soil at a
defined pressure, for example 5 kgf/cm.sup.2, may be used as means
for measuring the compactibility coefficient of the soil (elastic
constant referred to the loaded surface) the amount of set being
recorded and stored by a transducer on the baulk guide from the
initial contact to approximately 5 seconds after full load is
reached. To otain a rapid sequence of such measured values it is
possible for a plurality of test baulks of the kind heretofore
described to be disposed on the circumference of a hydraulically
operated measuring cylinder - individually freely rotatable over
corresponding angular ranges.
A plate or baulk, placed on the ground at a pressure of
approximately 1 kgf/cm.sup.2 and then retained in its vertical
position is suitable as transducer for measuring the shear strength
of the compacted soil. The measuring transducer in the more closely
defined sense is a dynamometer for defining that force, applied to
the said plate by the compacting apparatus or by the tractor, at
which the said plate begins to move (in the direction of the force)
relative to the adjacent soil surface. The barrel of a roller,
rolling with moderate pressure on the soil and driven by an
unbalance exciter, may be used for measuring the continuous
vibration impedance. In acceleration pick-up with a vertical
operating direction defines the accelerations of the measuring
roller and therefore also of the soil under the effect of the
alternating harmonic force transmitted under the effect of the
exciter; the ratio of these two magnitudes is the impedance of the
soil.
The pulse or impact impedance is the reciprocal of the
Laplace-transformed derivation of the weight function (referred
pulse response). The zones of minimum frequency, corresponding to
those time intervals from the pulse time at which the deformation
velocity becomes zero, that is to say, when the soil begins to
swing back, are of significance for a knowledge of the soil
characteristics. If the soil is hard-elastic, these periods will be
short. If on the other hand the soil characteristics vary from
plastic to plastic-flowing, these periods of time will be long to
practically infinite. The values may be measured by attaching a
velocity pick-up on a drop weight, the said velocity pick-up being
adapted to operate an integrating member from the time of impact to
the time at which its output signal becomes zero; the measured
value is the appropriate final value of said integrator.
Penetrometric soil properties can also be measured by a system
incorporating a cylinder which rolls under a certain thrust on the
soil, the cylinder barrel having teeth or spikes surmounted upon it
which, under the applied thrust, penetrate to a greater or lesser
depth into the surface of the soil. The penetration depth is
measured by a distance transducer, for example, as the distance
between the axis of such a spiked cylinder and a smooth cylinder,
guided axially parallel thereto and also rolling on the soil.
It is not usually possible to base the operation of soil compacting
apparatus which is to be suitable for any kind of material to be
compacted, on a knowledge of the characteristics of the controlled
system. It is therefore not possible to predict the sense in which
the operating characteristics of the apparatus, for example, the
unbalance, must be changed in the event of a deviation of the
measured soil characteristics from a set value in order to cause
such deviation to disappear. Modulation of the command variable in
conjunction with multipliers for automatically changing the control
characteristics will be utilized in the above described manner for
such apparatus. It is also possible for multi-purpose apparatus to
be provided which can be switched to different pre-programmed
control characteristics for the purpose of adaptation to different
materials if the effect of a change of operating characteristics on
the achieved compaction is known. Finally, it is also possible for
single-purpose machines to be provided which are intended for use
on soils with a uniform or rather similar relationship to one
operating characteristic and in which the regulating direction and
slope of regulating direction are designed and defined with respect
to the purpose of the apparatus. Finally, it is also possible for
leading measuring means to be provided, said means being
constructed as a measuring transducer in front of the compacting
apparatus or the first working member thereof for one or more of
the following soil-physical characteristics:
(a) Compactibility
(b) Water content
and that the signals of the leading measuring means may be applied
to the regulating means in the sense of disturbance-variable
feed-forward.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic perspective view of a dynamic soil
compacting apparatus according to the invention:
FIG. 2 is a signal flow diagram symbolically representing the
measuring and control system elements in the apparatus according to
the invention;
FIG. 3 is a schematic of a correlator used in the apparatus
according to FIG. 2;
FIG. 4 is a schematic showing a squaring element which may be used
for the correlator according to FIG. 3;
FIG. 5 schematically shows a rectifier adapted for suppressing
minimum values and as usable in the circuit of FIG. 4;
FIG. 6 is a side view of an embodiment for defining the moist bulk
weight by means of radio isotope measurement for use with soil
compacting apparatus according to the invention;
FIG. 7 is a front view of the embodiment of FIG. 6;
FIG. 8 is a front view of measuring means for the continuous
measurement of the dry bulk weight or of the water content of the
soil by means of an electrical measuring method;
FIG. 9 is a side view of apparatus for defining the compactibility
coefficient of the soil in soil compacting apparatus according to
the invention;
FIG. 10 is a front view of the apparatus of FIG. 9;
FIG. 11 shows a detail of the apparatus of FIG. 9;
FIG. 12 is a diagram explaining the method of operation of the
apparatus of FIGS. 9 to 11;
FIG. 13 is a schematic of a circuit employed in conjunction with
the apparatus of FIGS. 9 to 12;
FIG. 14 is a side view of measuring means for defining the shear
strength of the soil to be compacted in soil compacting apparatus
according to the invention;
FIG. 15 is a rear view of the measuring means of FIG. 14;
FIG. 16 is a plan view of the measuring means of FIGS. 14 and
15;
FIG. 17 is a side view of measuring means for defining the
continuous vibration impedance of the soil in soil compacting
apparatus according to the invention;
FIG. 18 is a front view of the measuring means of FIG. 17;
FIG. 19 is a schematic of the circuit used in conjunction with the
measuring means of FIGS. 17 and 18;
FIG. 20 is a side view of measuring means for defining the pulse or
impact impedance of the soil in soil compacting apparatus according
to the invention;
FIG. 21 is a front view of a detail of the measuring means of FIG.
20;
FIG. 22 is a diagram of the signal flow to explain the method of
operation of apparatus according to FIGS. 20 and 21;
FIG. 23 is a schematic of a circuit used in conjunction with the
measuring means of FIGS. 20 and 21;
FIG. 24 is a side view of further measuring means for soil
compacting apparatus according to the invention;
FIG. 25 is a front view of the embodiment of FIG. 24;
FIG. 26 is a schematic of a circuit used with the measuring means
of FIG. 24;
FIG. 27 is a side view of a further embodiment; and
FIG. 28 is a side view showing a modification of the embodiment of
FIG. 27.
DESCRIPTION OF SPECIFIC EMBODIMENTS
FIG. 1 shows a basic embodiment of the invention. The soil
compacting apparatus to be controlled in this case is a known
double vibratory roller 1, the rollers thereof forming compacting
elements. At its front it guides leading measuring means 3 mounted
on a frame 2 which may be pivoted upwardly. The measuring means
shown in FIG. 1 is not detailed. It may, for example, be provided
for measuring the compactibility of the soil being worked.
Auxiliary apparatus required for functioning of the measuring means
3 are disposed in the enclosed container 4, in particular the
electronic system required to this end.
At its rear the compacting apparatus 1 has trailing measuring means
6 mounted on a frame 5. This measuring means may comprise apparatus
for mesuring one or more of the seven soil characteristics
hereinbefore listed in subparagraphs (a) to (g) of the Background
And Summary of the Invention. The measured values generated thereby
either as such or in conjunction with the measured values provided
by leading measuring means 3 are processed to yield control signals
in apparatus disposed in the container 7 which is also provided
with setting means or controls 8 and indicating means 9 which are
in the field of view and within operating reach of the driver of
the apparatus. Furthermore, the signals supplied to the indicating
means 9 may also be utilized for generating the control signals for
automatic control or regulation, for example, of the traveling
speed of the compacting apparatus 1.
FIG. 2 is a general signal flow chart according to the basic idea
of the invention. The numeral 11 refers to a measuring means in
accordance with leading measuring means 3 of FIG. 1. The output
signal of said measuring means is supplied to a store 12 which
receives and maintains that signal until a succeeding measured
value is established. Another store 13 is associated with the
measuring means 14, which is a trailing measuring means such as
that illustrated at 6 in FIG. 1. A number of specific types of
measuring means usable for measuring means 14 is subsequently
discussed in connection with FIGS. 6-7, 8, 9-11, etc. Before use
the output signals from the sensor thereof are suitably processed
by a processing circuit, as for example FIG. 13. Store 13 receives
and maintains the measured values (actual value signal) from
measuring means 14 until the succeeding measured value is
established. The contents of the store 12 are transferred to an
adding stage 16 through a delay element 15, the delay period of
which corresponds to the time required for the apparatus to travel
over the distance between the leading and trailing measuring means.
The signals from the store 13 are also supplied to the
aforementioned adding stage. An adjustable fixed-value transmitter
17 generates the command signal. A generator 18 produces individual
squarewave pulses having a duration of, for example, 8 seconds.
Generator 18 is triggered through its starting input 19. The
outputs of the fixed-value transmitter 17 and of the genertor 18
are also supplied to the adding stage 16 through an adding element
20.
In terms of process control technology, the three inputs of the
adding stage 16 have the following significance. Data from the
store 13 represents the actual value of the automatic control. Data
supplied from the delay element 15 represents a form of
disturbance-variable feed-forward. The signal of the fixed-value
transmitter 17 corresponds to the command variable of the automatic
control and the output signal of the generator 18 corresponds to a
command variable feed-forward.
After being subjected to intermediate amplification in an amplifier
21, the output signal of the adding stage 16 is supplied to the
first input of a multiplier 22. The output thereof acts on the soil
compacting apparatus 24, like the one shown in FIG. 1, through a
converter 23 which, in terms of process control takes the form of a
final control drive, the said apparatus 24 by virtue of its
compacting function varying the soil 25 to yield the actual value
of the process control function as represented by measured signal
from the measuring means 14. The basic control circuit included in
FIG. 2 therefore comprises the units 14, 13, 16, 21, 23, 24 and 25.
In the simplest embodiment of the invention (for single-purpose
machines with manual control) the multiplier 22 may take the form
of an indicating instrument for the output signal of the
intermediate amplifier 21 and the converter 23 may take the form of
manual adjusting means like indicating means 9 and controls 8 in
the double vibratory roller 1 as shown in FIG. 1. The fixed-value
transmitter 17 in this embodiment will then also be replaced by a
mark on the indicating instrument. In single-purpose machines with
automatic control the output signal of intermediate amplifier 21 is
fed to the first input of the multiplier 22, the second input of
which is provided with a fixed voltage transfer signal (from a
transfer signal generating means, not shown) so that this component
transfers data to the converter 23 under fixed transfer conditions.
In multi-purpose machines the transfer characteristics of the
multiplier 22 are varied by a variation in the fixed voltage
supplied to the second input so that a plurality of discrete
characteristics are obtained.
In the embodiment for multi-purpose machines the second input value
of the multiplier 22 is formed in the following manner, utilizing
the square-wave generator 18. The lower input of the differential
amplifier 26 is supplied with the instantaneous value of the
command variable, formed by the adding amplifier 20, the second
input being supplied by a value of this quantity which is delayed
by the store 27. Corresponding conditions apply to the differential
amplifier 28 and the store 29, but in this case with respect to the
measured value signal from the measuring means 14 of the trailing
measuring means 6 instead of with respect to the command variable.
The output quantities of the differential amplifiers 26 and 28,
supplied to the further multiplier 30, therefore correspond to the
differences between the instantaneous value of command variable and
the measured (actual) value with respect to the values possessed by
these quantities at an earlier moment of time, defined by further
structural components which will be described hereinbelow. The
multiplier 30 forms an output signal which substantially
corresponds to the product of these two differences and which is
supplied to the input of a classifying stage 31. The product
signal, thus graded, is supplied through a controlled gate 32 to a
holding element 33 and from there to the second input of the
multiplier 22.
The controlled condition, as yet unevaluated, is tapped off from
the position designated with the letter a between the amplifier 21
and the first multiplier 22 and is supplied to a minimum value
limiting stage 34. The signal then passes through the succeeding
totalizing stage 35 to a pulse stage 36. A pulse b will occur at
the output of the pulse stage whenever the unevaluated controlled
condition a is exceeded by a defined amount which, in the sense of
automatic process control technology, may be described as a
permissible deviation. At first, this pulse will set the output of
the holding element 33 to a fixed value which is independent of the
remaining quantities of the control system; furthermore, the pulse
will also drive the gate 32 and start a timer 37 which defines the
duration of the command variable feed-forward. The stores 27 and 29
are reset when an output signal appears on the timer 37, the said
stores being set to receive signals for the measured value and the
command variable. Disappearance of the output signal of the timer
37 also causes the gate 32 to be driven to cut off. The pulse also
starts the generator 18 via the input 19 to form the command
variable feed-forward signal.
FIG. 3 is a basic system of the multipliers 22 and 30 employed in
the control system as shown in the flow chart of FIG. 2. The
voltages supplied to the two inputs 41 and 42 of such a multiplier
are supplied to an adding stage 43 and a differentiating stage 44
and from there via squaring stages 45 and 46 to a differentiating
stage 47. The function of such a stage is determined by the fact
that the pure squares of the input values cancel each other in the
terminating differentiating stage and the mixed products are added.
FIG. 4 shows a possible embodiment of the squaring stages. In this
case, the signal to be squared is first superimposed in an adding
stage 48 on the output signal of a saw tooth generator 49, the
frequency of said generator being higher by one order of magnitude
or more than the characteristic frequency of the signal which is to
be squared. The output signal of the adding stage 48 is supplied to
a rectifier stage 50 with minimum value suppression, so designed
that the suppressed zone corresponds to the sweep of the saw tooth
generator 49. The proportions of generator voltage of higher
frequency are filtered out from the square of the measuring voltage
thus obtained in the succeeding integrating stage 51. The squaring
function of such a stage is obtained by virtue of the fact that the
saw tooth voltage of the generator 49 cannot pass through the
rectifier 50 when the measuring voltage disappears, but if a
non-disappearing measuring voltage is superimposed, those peaks of
the generator voltage the amplitude of which corresponds to the
instantaneous value of the measuring voltage will pass through the
rectifier 50. The timing characteristics of the voltage peaks thus
produced on the output of the rectifier 50 represent similar
triangles the height of which corresponds to the measuring voltage.
According to a known principle of geometry, the areas of these
triangles, that is to say the charges transmitted by the said
pulses and therefore the voltages which appear across the
integrating capacitor, vary as the squares of the heights of the
triangles.
FIG. 5 show a possible embodiment of such a rectifier 50 with
minimum value suppression. Together with the push-pull amplifier 52
and the two rectifiers 53 it initially represents a known full-wave
rectifier. The half-wave voltages which appear across the working
resistors 54 of said rectifier are isolated from the stage out-put
56 within the limiting zone by means of zener diodes 55 and are
generally transferred to the output 56 only with that voltage
proportion by which they exceed the breakdown voltage of the zener
diodes 55.
FIG. 6 and 7 show an embodiment of trailing measuring means for
determining the moist specific gravity of the soil by radio isotope
measurment. The trailing measuring means are formed by in a
single-axle trailer formed by the wheels 61, the shaft 62 and the
drawbar 63. Two disc cams 64, the outer edge 65 of which is
circular over a wide angular zone and extends more closely to the
axis of the apparatus in the remaining angular zone, is coupled to
the shaft 62. A roller support 68, the supporting rollers 69 of
which are adapted to engage in the inner running surfaces of the
disc cams 64 is mounted on the surface probe 66 by means of a
powerful leaf spring 67. The counting apparatus 71 is mounted on a
pivoting support 70 on the shaft 62 adjacent to the aforementioned
disc cam 64, the counting pulses being supplied to said counting
apparatus 71 through a lead 72 from the probe 66. The roller
support 68 of the supporting rollers 69 is also provided with a
contact transmitter 72a from which a control signal is supplied to
the counting apparatus 71 when the disc cams 64 release the
supporting rollers 69 and the probe 66 is disposed freely on the
coil surface. In operation the disc cams 64 periodically raise the
surface probe 66, convey it forward and deposit it for a defined
period of time (dwell) on the soil surface. During this dwell
period of the probe 66 the input of the counting apparatus 71 is
rendered conductive by the signal of the contact transmitter 72a so
that the counting apparatus is able to transmit the counting rate,
corresponding to the moist specific gravity of the soil, through
the signal conductor 74 to the measuring and control system
elements according to FIG. 2.
FIG. 8 is an embodiment of measuring means which may be employed as
leading as well as trailing measuring means for continuously
determining the dry specific gravity or the water content of the
soil according to an electric measuring method. The measuring means
is also constructed in the form of a single-axle trailer, the four
running discs 81 also representing the measuring probes. Of these
four discs, the two inner running discs represent the voltage
probes; they are fixedly joined to each other by means of a
cylindrical support member 82 in which the battery-operated
electronic circuit 83 design is accommodated. The two coaxially
disposed outer current probes are guided by torsion-resistant and
flexible axle coupling elements 84 so that a uniform soil contact
of all four running discs 81 is obtained in conjunction with the
forces of the leaf springs 85 which act on the outer ends of the
axle. The signal, delivered in this embodiment through the slip
rings 86 and the signal conductor 87 corresponds to a current flow
through the outer probes required for a controlled and maintained
voltage between the inner probes and, as is known, is a direct
measure of the dry specific gravity of the soil when the water
content is known.
FIGS. 9 to 11 refer to an embodiment of trailing measuring mean for
determining the compactibility of a soil. The apparatus is
constructed as a two-axle trailer, the axle which leads in the
traveling direction being adapted to support a container 91 which
may be filled with water or building material in order to provide
adequate loading of the said axle. The two identically constructed
axles of this apparatus have the following construction. Separate
wheel discs 94 run on the right-hand and left-hand sides
respectively of shafts 93 which are fixedly disposed at the frame
92 of the trailer. Thrust members in the form of tiltable rams 95
are disposed at equal distances from each other on the
circumference of each said wheel disc. The wheel discs 94 are
positively coupled to each other through a hollow shaft 96 and
through a chain drive 97. Centrally on each shaft 93, the vehicle
is provided with a smooth roller 98, having a hollow boss 99 on
both sides which surrounds the hollow shaft 96 and which is coupled
thereto through a flange 100, a universal joint 101 and a radius
rod 102, the hollow shaft 96 being freely rotatable in the bearing
103 of the radius rod 102. The radius rod 102 supports a gear rim
104 in the shape of a circular sector and adapted to mesh with a
gear wheel 105 the shaft of which is provided with measuring means,
not shown, in the form of a distance transmitter.
This apparatus functions in the following manner. Under the effect
of material filled into the container 91, the weight of said
material acting through the frame 92 and the wheel axle 93 causes
the front axle rams 95 located in the respective lowest position on
the running discs 94 to penetrate into the soil, while the smooth
roller 98 is guided by the radius rod 102 and rolls on the
undisturbed soil surface. The angular position of the gear wheel
105 or the output of the measuring means driven thereby therefore
represents a measure of the depth to which the rams 95 penetrate
into the soil. Positive coupling of the front and rear trailer axle
simultaneously provides a measured value for the penetration of
rams 95 on the rear wheel discs at a position of the soil on which
corresponding rams of the leading wheel discs had previously
acted.
FIG. 12 illustrates these relations in a simple thrustset diagram.
Staring from point 111 of this diagram, the curve 112 shows the
penetration of rams on the loaded leading wheel discs into the soil
to a maximum value 113 (set value) S1) which corresponds
substantially to the traveling phase illustrated in FIG. 9. As the
measuring apparatus continues to travel, the soil loading is
reduced at this position and the set is reduced in accordance with
the curve section 114 to a value S2 which is then measured by the
rear wheel discs of the measuring trailer. The ratio of maximum set
S1 to permanent set S2 or the reversible set S1- S2, evaluated by
reference to the maximum loading, may be used to indicate the
degree of compaction of the respective soil 25 and to form suitable
measured values to serve the function of the signals supplied by
measuring means 14 of the measuring and control system as shown in
FIG. 2.
FIG. 13 shows a processing circuit for forming such measured
values. The signal derived from the leading vehicle axle, reaches
the input 121 of the circuit, the corresponding signal from the
rear axle reaching the input 122.
These measured values are supplied to maximum-value stores 122a and
from there pass to the junctions 123. This is utilized, in a first
processing branch, to indicate the ratio through the angular
position of the pointer 127, mounted on the potentiometer spindle
of the double-wiper potentiometer 126 which is driven by the
servomotor 124 through the differential amplifier 125. In a second
processing branch the voltages are transferred from the junctions
123 through coefficient adjusting means 128, the characteristics of
which are set by the loading represented by the container 91, to a
differential amplifier 129 and from there to an indicating
instrument 130. The embodiment also incorporates a stepping switch
131, of which only two switching positions are shown in FIG. 13 and
which generally contains as many switching positions as there are
impressions of the leading trailer axle produced in the soil
between said axle and the trailing in accordance with the length of
the trailer. According to FIG. 10, the stepping switch is
controlled by pulse transmitters 106 which are mounted on the
vehicle frame 92 so that cyclic indexing of the stepping switch
occurs always at the moment at which the next rams on the leading
trailer axis makes contact with the soil (in FIG. 10 the said pulse
transmitters are disposed on the interior of the frame 92 near the
periphery of the leading wheel disc). The pulse transmitters 106
may take the form of reed switches which are operated by magnets
disposed on the exterior of the wheel discs 94 between the rams 95.
In an additional switching deck 132, according to FIG. 13, these
pulses are additionaly fed to the cancelling inputs of the
maximum-value stores which are connected during the preceding pulse
interval.
FIGS. 14 to 16 show an embodiment of trailing measuring means for
determining the shear strength of the compacted soil. The means
comprise a thrust plate 141, serrated on the underside. It is
pulled by the steered roller 145 of the leading compacting vehicle
from a trail rope 142 and through a damped spring 143 and force
sensor 144. The thrust plate 141 supports an axle bearing 146 with
an axle 147 on which two rigidly coupled running wheels 148 are
eccentrically disposed so that when the thrust plate 141 is at
rest, the torgue produced by the gravitational force of the running
discs 148 causes these to rotate forwardly in the traveling
direction of the compacting apparatus so that they bear on the soil
laterally adjacent of the thrust plate. The force sensor 144
measure the force transmitted through the trail rope 142 to the
thrust plate 141. This force increases while the spring 143 is
extended until the shear strength of the soil below the thrust
plate 141 is exceeded. At this moment the signal amplitude of the
force sensor 144 will drop spontaneously accompanied by the
beginning of a rolling motion of the running disc 148 which raise
the thrust plate 141 from the soil and, in accordance with their
diameter, move the said plate forwardly in the traveling direction
by at least one plate length and then once again place it on the
soil. The controlled variable is the peak value of the signal
emitted by the force sensor 144, said peak value being transferred
to a store in accordance with store 13 of FIG. 2.
FIGS. 17 and 18 show an embodiment of trailing measuring means for
determining the continuous vibration impedance of the compacted
soil. The said measuring means comprise a single-axle roller drawn
by the compacting apparatus. In addition to its drawbar 151, said
single-axle roller incorporates a loading bar 152, journaled on the
roller axle and supporting on its upper platform 153 a directional
force generator 154 the principal operative direction of which is
vertical. The numeral 155 refers to the drive for the
aforementioned directional force generator while the numeral 156
refers to an angle position transmitter, rigidly coupled to the
rotor shafts of the generator. Near each of the roller axle ends
the loading bar 152 is also provided with an acceleration pick-up
157 with a vertical operative direction and, centrally below the
directional force generator, an elongation transducer 158 disposed
in a reduced cross-sectional zone.
FIG. 19 shows an embodiment of the associated processing circuit.
The signals of the acceleration pick-ups 157 are supplied to the
inputs 169 and 170 of the aforementioned circuit, the summated
voltage of said signals being tapped off by an adjustable
potentiometer 171 which connects the inputs 169, 170. The summated
voltage is integrated by an integrator 172 and supplied to the
inputs of the controlled rectifiers 173. The signal of the
elongation transducer 158 is supplied to the input 174, said signal
being supplied to the inputs of the controlled rectifier 176 after
having superimposed upon it a portion of the summated voltage
obtained from the tapping of the adjustable potentiometer 175. The
control voltages of the said rectifiers are derived by means of
pulse-forming stages, not shown, from the output signals of the
phase angle transmitters 156 and are supplied to the circuit
through the input sockets 177 and 178. These two square-wave
voltages are phase-displaced relative to each other by one quarter
of their cycles. The present embodiment dispenses with phase data
relating to the continuous vibration impedance and merely responds
to its total amount. To this end, the output voltages of the
controlled rectifiers 173 and 176 are supplied in pairs to separate
co-ordinate computers 179, the output voltage of which varies with
respect to the output voltages of the controlled rectifiers 173 and
176 in the same way as the hypotenuse of a right-angle triangle
varies with the length of the short sides thereof. The voltages
thus obtained are supplied through a range selector 180, covering
both channels, to quotient indicating means comprising
potentiometer 181 of the kind already described with reference to
FIG. 13. The position of the pointer 182 thus corresponds to the
amount of continuous vibration impedance of the compacted soil at
the frequency of the directional force generator 154 and forms the
measured value of the measuring means 14 of the control system of
FIG. 2 or, respectively, as indicated by indicating means 9 of the
double vibratory roller 1 in FIG. 1.
FIGS. 20 and 21 refer to an embodiment for trailing measuring means
adapted to obtain a measured value which is characteristic for the
pulse or impact impedance of the compacted soil. The numeral 191
refers to a greatly simplified rearward part of compacting
apparatus 24; this supports tamping means in which the drop weight
192 is mounted on a bracket 193 at one end of a guide rod 194 and
may be raised by means of a lever 195. Lever 195 is rigidly coupled
to a gear wheel 196 adapted to mesh with a gear wheel 197 the tooth
system of which is sub-divided into segments. The guide rod 194
hinged to the lever 195, is guided in the traveling direction by a
spring damping element 198. If the segmented gear wheel 197 is
driven at a moderate and constant angular velocity, it will first
raise the drop weight 192 on the guide rod 194, by virtue of a
rotation of the gear wheel 196 and the lever 195 coupled thereto,
and then allow it to drop instantaneously when the gear wheels 197
and 196 are out of mesh. During the contact phase the spring
damping element 198 absorbs the increasing distance resulting from
the traveling motion of the compacting apparatus 24 which will be
compensated for during the succeeding lift period of the drop
weight 192. An acceleration pick-up 199 having a vertical operating
direction is disposed on the drop weight below the bracket 193.
The kinematic conditions accompanying operation of the
aforementioned measuring means are illustrated in FIG. 22. The
upper diagram shows the output signal of the acceleration pick-up
199 as a function of time, corresponding to the difference between
effective acceleration and gravitational acceleration. The first
part of the curve to the moment of time 200 therefore corresponds
to the dropping motion of the drop weight 192. At the moment of
time at which contact is made with the soil, a substantially
upwardly directed acceleration occurs but rapidly decreases and,
after moment of time 201, and in accordance with the soil
characteristics, returns in a more or less damped oscillation to
the initial value, the said soil characteristics being of no
interest for the measured value to be obtained in this context.
The lower diagram represents a velocity signal as derived from the
upper diagram. This signal is constant for a first period of time,
that is to say during the trajectory phase, said constant level
corresponding to the impact velocity of the drop weight 192. This
variable tends towards zero in accordance with the substantial
positive acceleration after moment of time 200, the zero line being
reached at the moment of time 202 and then being exceeded which is
of no interest in the present case.
FIG. 23 relates to an embodiment of a related processing circuit.
The signal of the acceleration pick-up 199 is supplied to the input
211. In the main branch of this system the signal is supplied to
the integrating stage 212 which is supplied with its initial value
from the dc voltage generator 213 through a coefficient adjuster
214. The adjuster 214 is set so that the initial value corresponds
to the impact velocity as derived from the drop height of the drop
weight 192. The succeeding stage 215 performs signal amplification
with a high gain and peak limitation and therefore functions as a
signum. The store 217 is supplied from the following
differentiating stage 216. After processing by the negating circuit
218 the store output signal is supplied to a further integrator 220
via AND gate 219. The output integrator 220 appears on the
indicating instrument 221 which corresponds to indicating means 9
at the double vibratory roller 1 in FIG. 1. The AND gate 219 on the
other hand is controlled by the acceleration signal from a limiting
amplifier 222 so that integration by the integrator 220 will
proceed only if the acceleration signal is positive. This ensures
that in correspondence with the lower diagram in FIG. 22
integration will only occur during the period of time between
moments 200 and 202. After moment of time 202, the pulse input 223
of the circuit is supplied, by means not shown, with a cancelling
pulse for the store 217 and for resetting the integrator 220 to the
initial value zero. The signal applied to indicating instrument 221
also may be applied to the measuring and control system shown in
FIG. 2 as the measured value of the measuring means 14.
FIGS. 24, 25 and 26 show a further embodiment for trailing
measuring means. The measuring means comprise a single axle roller,
trailing the compacting apparatus 24. A frame 230 is journaled on
theaxle trunnions and, at both sides, supports acceleration pickups
231. The signals of these acceleration pick-ups are supplied to the
two inputs 232 of the processing circuit shown in FIG. 26 and
tapped off from an adding potentiometer 233 in the form of a
summated voltage, are then rectified in the stage 234 and supplied
to an amplifier 235 with multipoint characteristics. The following
stages in the circuit comprise basically classifying means,
indicating means 236 for the individual grades driven by timing
elements (comprising a ramp generator 238, an integrator 239 and a
square wave generator 237) which suppress the indication of a
respective grade value if the same is not repeated within a given
period of time. The signals at indicating means 236 which may serve
as indicating means 9 in the double vibratory roller 1 as shown in
FIG. 1 may be supplied as the measured values of the measuring
means 14 the measuring and control system as represented in FIG.
2.
FIG. 27 shows an embodiment for of trailing measuring means for
determining the propagation conditions of surface waves on the
compacted sub-grade. The numeral 241 refers to single axle roller
241 identical in construction with the measuring means as
illustrated in FIGS. 17 and 18 except for the measuring roller 243.
Light-weight measuring roller 243 is provided in vertical
configuration above the roller axle and on both sides with separate
acceleration pick-ups 244 of vertical operating direction. The
roller is drawn by means of a drawbar 242. Reference may also be
made to FIG. 19 as regards the associated processing circuit,
however the superimposing element of that circuit is omitted and
the input is connected directly to the two controlled rectifiers.
The indication provided by the pointer will then correspond to the
amount of the ratio of the vertical vibration velocity of the soil
occurring at the position of measuring roller 243 to the excitation
intensity introduced by the roller 241.
FIG. 28 shows a simplification of the embodiment in the event that
the compacting apparatus is a vibration apparatus adapted to
operate top load mode, for example a duplex roller. The angular
position transmitter 196 as in FIG. 20 is mounted on the unbalance
exciter of the said compacting apparatus. The output signals of the
transmitters are supplied to control inputs 177, 178 of the
rectifiers 173, 176; see FIG. 19.
* * * * *